Investing today for tomorrow: pre- and post-weaning nutrition of the dairy calf
March 8, 2026
Early-life nutrition remains one of the most powerful determinants of lifetime performance in the dairy herd. This message has been the cornerstone of recent calf rearing meetings led by CAFRE Adviser, Wilson Marshall, across County Armagh. Calf health, housing, nutrition and management were all covered.
Chris Keys, Armagh Business Sustainability Group participant, remarked “stacking as much as possible in the calf’s favour early in life will give it the best start possible”.
The metabolic and structural development that occurs in the first weeks of life is rapid and highly responsive to nutritional management. As a result, the period from birth to twelve weeks represents a unique window in which targeted feeding strategies can influence growth, immune competence, rumen development, and ultimately the heifer’s ability to reach breeding weight on time and calve down at 22-24 months.
Pre-Weaning: The Science of Early Nutrition Management
Colostrum remains the most critical feed a calf will ever receive. High-quality colostrum (25%+ Brix Value) delivered within two hours post-calving provides immunoglobulins, growth hormones, prebiotics, antibacterial peptides and vital energy to enhance nutrient absorption and support early metabolic development. Achieving adequate passive transfer can be a challenge on many farms, and variability in colostrum quality underscores the importance of routine Brix testing, hygienic handling and rigorous colostrum management protocols.
Once calves transition to whole milk or milk replacer, the focus shifts to consistency and nutrient supply. Higher planes of nutrition in the pre-weaning period have been repeatedly shown to improve average daily gain, reduce morbidity, and enhance lifetime performance. Feeding programmes delivering 750-900g of milk powder equivalent per day – provided at the correct temperature and on a routinely schedule – support growth and gastrointestinal stability. The metabolic demands of a pre-weaned calf are high, and underfeeding during this stage can limit growth potential that cannot be recovered. Parallel to liquid feeding, the introduction of starter feed plays a central role in rumen development. Fermentation of starch and sugars within starter concentrate produces volatile fatty acids, particularly butyrate, which drives rumen papillae growth and functional maturation of the rumen wall. Offering small amounts of fresh, palatable starter from the first week, alongside unrestricted access to clean water, encourages intake and accelerates rumen adaptation. This early development of rumen is essential for a smooth weaning transition.
Weaning: A Physiological Transition
Weaning is often treated as a management milestone however as Wilson Marshall has illustrated to his Business Sustainability group members- ‘it is more than just a calendar event and biologically it is a transition from a monogastric-like digestive system to a functioning ruminant’. A key determinant of readiness is solid feed intake. Once calves consistently consume 1-1.5kg of starter daily, their rumen is sufficiently developed to transition to lower milk volumes. A gradual milk stepdown over 10-21 days minimises the risk of growth checks, as abrupt weaning can lead to reduced intakes, increased stress, and heightened susceptibility to respiratory disease. Avoidance of additional stressors such as disbudding, regrouping or environmental challenges during this period is critical. Notably through all BSG meetings members heard of the importance of avoiding cold stress in calves to prevent growth setbacks.
Post-Weaning: Sustaining Momentum and Avoiding the Growth Dip
The post-weaning period is where many systems inadvertently lose the gains achieved earlier. Calves require a diet that maintains energy density and protein supply while supporting continued rumen development. While milk feeds the calf in the pre-weaning phase, concentrates feed the rumen for the duration of rearing. Therefore, starter should remain the primary post-weaning feed until calves reach around 100-120kg, at which point a transition to a grower ration becomes appropriate. Diets containing 16-18% crude protein with good digestibility support frame growth and muscle deposition, while careful forage introduction helps stabilise rumen pH without depressing concentrate intake.
Environmental and social factors also exert a strong influence on post-weaning performance. Ventilation, stocking density, and group stability all affect respiratory health and feed efficiency. Regular weighing or weigh-band monitoring provides an objective measure of progress and allows early intervention if growth rates begin to plateau. The goal is to maintain a smooth, uninterrupted growth curve, avoiding the common post-weaning slump that can delay age at first service.
Long-Term Impact: Why Early Nutrition Matters
The benefits of optimising early-life nutrition extend far beyond the calf rearing phase. Heifers that double their birthweight by weaning and maintain strong growth post-weaning are more likely to reach breeding targets on time, calve earlier, and produce more milk in their first lactation. Research consistently links higher pre-weaning growth rates with enhanced mammary development and increased lifetime yield potential, with some studies suggesting an additional 1,000 litres in the first lactation where early growth targets are met. Epigenetic programming has also been an area of recent research whereby it is thought that early-life nutrition influences calf gene expression without altering DNA sequences. Notably, epigenetic programming is particularly sensitive in the first few days and weeks of life. Therefore, nutritional input during this time can permanently influence traits like immunity, metabolism and growth. Economically, the return on investment from well managed calf nutrition is substantial, making it one of the most cost-effective areas for improving overall farm performance. Throughout these recent BSG calf rearing meetings Learnings were successfully implemented by numerous BSG members who acted by increasing calf milk replacer and liquid volumes of milk fed, to further accelerate daily liveweight gains and cope with periods of cold stress.
